As a follow up to my own post, in the hope that the info may be useful to others, I decided to get a second opinion from a CI dealership on this fault and found it wasn't the relay panel, which would have cost me around £250 plus labour to replace.

The problem was a blown 40 Amp in line blade fuse situated next to the charger unit under the driver's seat. Cost of replacement 99p.

My thanks to Malcolm's Motorhomes of Stoke-on-Trent for their time and effort in locating and fixing the problem that the independent service engineer who first checked it had missed. The labour cost for this was very cheap by comparison with replacing the relay box, which wouldn't have solved the problem anyway.

'Aren't you happy just to be alive? Anything's possible' - Pulp, 'Dishes'

Well thats good news. Glad you got it sorted.
Im surprised no one answered your original post and suggested doing it. There are usually loads of folk willing to help on here . It must have been a quiet day
Who knows it may help us at sometime too as we have a CI .
Bev